usb_hid uses undocumented cbuf API

Description

The usb_hid input driver uses an undocumented cbuf kernel API on R5 (see
src/add-ons/kernel/drivers/input/usb_hid/hid.h). This API is different from the
cbuf implementation that is present in the Haiku kernel. It is therefore not
possible to build the usb_hid driver with TARGET_PLATFORM=haiku. I defined the
following to get it to build: